Battery pack and battery pack manufacturing method

Abstract

In a laser welding step, a laser beam is irradiated fin a thickness direction of an external terminal from a side of a front surface of a bus bar toward a space. This irradiation melts a separated portion of the external terminal, i.e., a portion located apart from the insulating part by the space between the insulating part and the separated portion in the thickness direction, and an opposed portion of the bus bar, i.e., a portion opposed to the space via the separated portion in the thickness direction, thereby forming a welded portion including the separated portion and the opposed portion melted together.

What is claimed is: 
     
       1. A method for manufacturing a battery pack, the method comprising:
 providing a bus bar made of metal and formed in a plate shape,
 preparing a plurality of cells to be used in the battery pack, by providing each of the plurality of cells with: 
 a metal cell case, 
 an external terminal made of metal, formed in a plate shape, and placed on an outside of the cell case, and 
 an insulating part made of resin having an electrical insulation property and interposed between a front surface of the cell case and a back surface of the external terminal to electrically insulate the cell case and the external terminal from each other, 
 the external terminal including a separated portion to be placed apart from the insulating parts of the plurality of cells in a thickness direction of the external terminal by a space intervening between the separated portion and the insulating part; 
 
 the separated portion being space apart from a swaged part that electrically connects the external terminal to a portion that is connected to an electrode body in the cell;
 placing the bus bar on a front surface of an external terminal of a first cell of the plurality of cells apart from the swaged part so that a part of the bus bar becomes an opposed portion opposed to the space in the thickness direction of the external terminal of the first cell of the plurality of cells by interposing the separated portion of the external terminal of the first cell of the plurality of cells; and 
 laser welding the opposed portion of the bus bar to the separated portion of the external terminal of the first cell of the plurality of cells; 
 wherein the laser welding includes irradiating a laser beam from a side of a front surface of the bus bar toward the space in the thickness direction of the external terminal of the first cell of the plurality of cells to melt the opposed portion of the bus bar and the separated portion of the external terminal of the first cell of the plurality of cells to form a welded portion at which the separated portion and the opposed portion are welded together, the welded portion being a portion at which the external terminal of the first cell of the plurality of cells and the bus bar are welded together, the welded portion being configured to extend in the thickness direction from the front surface of the bus bar toward the back surface of the external terminal of the first cell of the plurality of cells, and the welded portion being located apart from the insulating part of the first cell of the plurality of cells by the space intervening therebetween in the thickness direction of the external terminal, of the first cell of the plurality of cells, and 
 
 wherein the external terminal of the first cell of the plurality of cells includes a terminal recess having an opening in the back surface of the external terminal of the first cell of the plurality of cells,
 the terminal recess being configured to be recessed in a direction away from a front surface of the insulating part of the first cell of the plurality of cells, the front surface facing the back surface of the external terminal of the first cell of the plurality of cells, and 
 the space being an enclosed space defined by the terminal recess of the external terminal of the first cell of the plurality of cells and the front surface of the insulating part of the first cell of the plurality of cells that closes the opening of the terminal recess by contact with the back surface of the external terminal of the first cell of the plurality of cells. 
 
 
     
     
       2. The method for manufacturing a battery pack according to  claim 1 , wherein the laser welding includes performing penetration laser welding to make a molten metal portion melted by irradiation of the laser beam so as to extend from the front surface of the bus bar to the space of the first cell of the plurality of cells to form the welded portion extending from a front surface of the opposed portion of the bus bar to a back surface of the separated portion of the external terminal of the first cell of the plurality of cells. 
     
     
       3. The method for manufacturing a battery pack according to  claim 1 , wherein
 the external terminal of the first cell of the plurality of cells includes a terminal protruding portion protruding from the front surface thereof, 
 the bus bar includes a concave bus-bar recess allowing the terminal protruding portion of the first cell of the plurality of cells to be fitted therein, and 
 the placing includes placing the bus bar on the front surface of the external terminal of the first cell of the plurality of cells while making the terminal protruding portion thereof fit in the bus-bar recess. 
 
     
     
       4. A battery pack comprising:
 a plurality of cells, each of the plurality of cells including a metal case and an external terminal made of metal, formed in a plate shape, and placed on an outside of the cell case; and 
 a bus bar made of metal and formed in a plate shape, the bus bar being placed on and welded to a front surface of an external terminal of a first cell of the plurality of cells, and placed apart from a swaged part that electrically connects the external terminal to a portion that is connected to an electrode body in the cell, 
 wherein each of the plurality of cells further comprises:
 an insulating part made of resin, having an electrical insulation property, and interposed between a front surface of the cell case and a back surface of the external terminal to electrically insulate the cell case and the external terminal from each other, 
 
 wherein the battery pack includes a welded portion, at which the bus bar and the external terminal of the first cell of the plurality of cells are welded together, the welded portion being configured to extend in a thickness direction of the external terminal of the first cell of the plurality of cells, from a front surface of the bus bar toward the back surface of the external terminal of the first cell of the plurality of cells, and
 the welded portion is located apart from the insulating part of the first cell of the plurality of cells by a space intervening therebetween in the thickness direction of the external terminal of the first cell of the plurality of cells, the space being spaced apart from the swaged part, 
 
 wherein the external terminal of the first cell of the plurality of cells includes a terminal recess having an opening in the back surface thereof,
 the terminal recess being configured to be recessed in a direction away from a front surface of the insulating part of the first cell of the plurality of cells, the front surface facing the back surface of the external terminal of the first cell of the plurality of cells, and 
 the space of the first cell of the plurality of cells is an enclosed space defined by the terminal recess of the external terminal of the first cell of the plurality of cells, and 
 the front surface of the insulating part that closes the opening of the terminal recess of the first cell of the plurality of cells by contact with the back surface of the external terminal of the first cell of the plurality of cells. 
 
 
     
     
       5. The battery pack according to  claim 4 , wherein
 the external terminal of the first cell of the plurality of cells includes a separated portion located apart from the insulating part of the first cell of the plurality of cells in the thickness direction by the space intervening between the external terminal and the insulating part of the first cell of the plurality of cells, 
 the bus bar includes an opposed portion opposed to the space of the first cell of the plurality of cells by interposing the separated portion in the thickness direction of the external terminal of the first cell of the plurality of cells, and 
 the welded portion at which the separated portion and the opposed portion of the first cell of the plurality of cells are welded together is configured to extend from a front surface of the opposed portion to a back surface of the separated portion of the first cell of the plurality of cells. 
 
     
     
       6. The battery pack according to  claim 4 , wherein
 the external terminal of the first cell of the plurality of cells includes a terminal protruding portion protruding from the front surface of the first cell of the plurality of cells, 
 the bus bar includes a concave bus-bar recess allowing the terminal protruding portion of the first cell of the plurality of cells to be fitted therein, and 
 the external terminal of the first cell of the plurality of cells and the bus bar are welded to each other while the terminal protruding portion of the first cell of the plurality of cells is fitted in the bus-bar recess.